LinkedList vs ArrayList in Java Tutorial - Which Should You Use?

Introduction

This tutorial explores the differences between LinkedLists and ArrayLists in Java, highlighting when to use each data structure. Understanding these two collections is crucial for optimizing performance in Java applications, especially when dealing with various data manipulation tasks.

Step 1: Creating a LinkedList and an ArrayList

To start, let's create a LinkedList and an ArrayList for storing names.

Creating a LinkedList

1. Import the LinkedList class:

   import java.util.LinkedList;
   

2. Create a LinkedList instance:

   LinkedList<String> namesLinkedList = new LinkedList<>();
   

Creating an ArrayList

1. Import the ArrayList class:

   import java.util.ArrayList;
   

2. Create an ArrayList instance:

   ArrayList<String> namesArrayList = new ArrayList<>();
   

Step 2: Adding Elements to the Lists

Both LinkedList and ArrayList allow you to add elements in a similar manner.

Adding to a LinkedList

• Use the add method:

  namesLinkedList.add("John");
  namesLinkedList.add("Paul");
  namesLinkedList.add("George");
  

Adding to an ArrayList

• Use the add method similarly:

  namesArrayList.add("John");
  namesArrayList.add("Paul");
  namesArrayList.add("George");
  

Step 3: Accessing Elements

Accessing elements is straightforward in both data structures.

Accessing from LinkedList

• Use the get method, remembering that indices are zero-based:

  String name = namesLinkedList.get(2); // Retrieves "George"
  

Accessing from ArrayList

• The same method applies:

  String name = namesArrayList.get(2); // Retrieves "George"
  

Step 4: Understanding Performance Differences

Performance is a key consideration when choosing between LinkedLists and ArrayLists.

ArrayList Performance

• Random Access: Fast retrieval of elements due to underlying array structure (constant time complexity).
• Insertion/Deletion: Slower, as it requires shifting elements when adding/removing items.

LinkedList Performance

• Random Access: Slower, as it requires traversing nodes to access elements (linear time complexity).
• Insertion/Deletion: Faster, as it only involves changing pointers without shifting elements.

Step 5: When to Use Each Data Structure

Choosing the right data structure depends on your application's needs.

Use ArrayList When

• You need fast access to elements.
• The list size is relatively stable, with few insertions or deletions.

Use LinkedList When

• You frequently add or remove elements, especially at the beginning or end of the list.
• The size of the list changes dynamically.

Conclusion

In summary, both LinkedLists and ArrayLists are useful in Java, each with its strengths and weaknesses. Understanding when to use each can significantly enhance the performance of your applications. If you're dealing with frequent data retrieval, opt for ArrayList. For dynamic lists that require frequent insertions and deletions, choose LinkedList. Experiment with both data structures in your Java projects to see how they fit your specific needs.